This invention relates in general to antioxidants and in particular to processes for the preparation of alkyl ester antioxidants containing a hindered phenol moiety.
Known methods for the production of higher alkyl hydroxy alkylphenyl alkanoate esters require several steps usually including transesterification of a lower alkyl ester to a higher ester. The lower alkyl esters are first prepared from a hindered phenol and methyl acrylate in a fashion which either produces large amounts of by-products or requires substantial amounts of suitable solvents to remove the by-products. Other known methods require very slow reaction between the methyl acrylate and the hindered phenol so as to circumvent the shortcomings of the previously mentioned methods. However, these methos require the very slow addition to methyl acrylate to the reaction mixture which detracts from the economy of the process. Also the reaction rates are slow despite the use of small amounts of alcohols or solvents. Suggestions have been made to improve the conversion of the prior art processes but a process is needed which provides a good conversion of high purity product with a relatively fast reaction.